De Zoetwaterneriet Theodoxus fluviatilis fluviatilis (Linnaeus, 1758) na 50 jaar levend teruggevonden in Maastricht, Limburg

The distribution area of the River nerite Theodoxus fluviatilis fluviatilis (Linnaeus, 1758) in the Netherlands has shrunken considerably over the last half century. Hence, in 2004 the species was classified as ‘vulnerable’ on the Dutch Red list. In the province of Limburg, where up to 1947 the River nerite still occurred in at least eight municipalities, the number of observations of live specimens dropped to zero after 1970. However, on 30 March 2018 live snails were discovered in a dammed branch of the river Maas in Bosscherveld, a northern quarter of Maastricht, capital of the province of Limburg. Perhaps improved quality of water in the river Maas may explain the return of this species.